Light micrograph of the large bowel (colon) showing the mucosa (green), submucosa (orange) and muscularis externa (yellow). The mucosa has elongated tubular glands with mucus-secreting goblet cells stained green. Loose connective tissue of the submucosa shows occasional lymphoid aggregations (grey stain). The muscularis externa consists of two layers of smooth muscle an inner circular and an outer longitudinal layer. Paraffin section, alcian blue and van Gieson's stain. Magnification: x40 when width printed at 10cm.